thermoking apu no heat

[Yauchout]

i am not sure if anyone here is familiar with repair on thermoking apu's or Eberspächer bunk heaters but the heat has stopped working on my thermoking apu if i restart the apu (power it off then back on) it will start blowing heat for 30-40 seconds then quit. when i plug the apu it into my laptop the thermoking software shows no error codes or problems shows a cabin temp of 65 and a setpoint of 78 if i go into diagnostics mode and select the heater test it will complete the entire 15 minute diagnostic blowing heat the entire time on high without any problems.